Research backs ‘Mediterranean diet’

A new study has discovered the Mediterranean diet with its characteristic “healthy fat” olive oil, does not lead to significant weight gain when compared to low-fat diets.

According to the research published in The Lancet Diabetes and Endocrinology journal, current health guidelines recommending a low-fat, low-calorie diet “create unnecessary fear of healthy fats present in a Mediterranean diet, which have known health benefits.”

The scientists says there is accumulating evidence suggesting total fat content is not a useful measure of the harms or benefits of food.

“More than 40 years of nutritional policy has advocated for a low-fat diet but we’re seeing little impact on rising levels of obesity,” says lead author of the latest research, Dr Ramon Estruch, from the University of Barcelona in Spain.

“Our study shows that a Mediterranean diet rich in vegetable fats such as olive oil and nuts had little effect on bodyweight or waist circumference compared to people on a low-fat diet. The Mediterranean diet has well-known health benefits and includes healthy fats such as vegetable oils, fish and nuts. Our findings certainly do not imply that unrestricted diets with high levels of unhealthy fats such as butter, processed meat, sweetened beverages, deserts or fast-foods are beneficial,” Dr Estruch said.

How the study worked

The study took place in 11 hospitals in Spain during 2003-2010 and included 7,447 participants (men and women) aged 55-80 who were randomly assigned to one of three groups – an unrestricted-calorie Mediterranean diet rich in olive oil, an unrestricted-calorie Mediterranean diet rich in nuts, or a low-fat diet where the advice was to avoid all dietary fat.

Adherence to the diets was described as “good” and monitored by questionnaires for all participants and by taking blood and urine samples in a random subgroup. All participants were at high cardiovascular risk or had type 2 diabetes. More than 90 per cent were overweight or obese.

After five years, total fat intake had decreased in the low-fat diet group (from 40 per cent to 37.4 per cent) and had slightly increased in both Mediterranean diet groups (40 per cent to 41.8 per cent in olive oil; 40.4 per cent to 42.2 per cent in nuts). The percentage of energy intake from protein and carbohydrate decreased in both Mediterranean diet groups.

On average, participants in all three groups lost some weight with the greatest weight loss seen in the Mediterranean diet with olive oil group (0.88 kg weight reduction in the olive oil group, compared to 0.60 kg for the low-fat diet group and 0.40 kg for the nuts group). There was an increase in waist circumference in all three groups with the greatest increase seen in the low-fat diet group (1.2 cm increase for the low-fat diet group).

Despite the recent cluster in research from health professionals saying fat should not be avoided, other health professionals have criticised this stance.